<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			.nav {
				display: flex;
				width: 1200px;
				margin: 0px auto;
				justify-content: space-around;
				background-color: yellow;
			}
			
			.div-left{
				background-color: #f00;
				width: 400px;
				height: 30px;
			}
			
			.div-right {
				background-color: #0f0;
				width: 300px;
				height: 30px;
			}
			
		</style>
	</head>
	<body>
		<header>
			<nav class="nav">
				<div class="div-left"></div>
				<div class="div-right"></div>
			</nav>
		</header>
	</body>
</html>